1. Field of the Invention
The present invention relates to a network system such as STM (Synchronous Transfer Mode) and ATM (Asynchronous Transfer Mode), and more specifically, relates to a technique for setting a path in the network.
2. Description of the Related Art
With the STM and ATM network, connection is preset, and data (cell) is transmitted on the preset connection. As the connection, there are PVC (Permanent Virtual Connection) and SVC (Switched Virtual Connection).
The PVC is a connection fixedly set between nodes, and is set when an manager (operator) of network uses it for a medium or long term like a private line, depending on the application of the network. The PVC is set by a manual operation of the manager (the operator inputs the necessary information to a node (switching station) by hand).
The SVC is a dynamic virtual connection. When an address of destination is specified, an relay route is selected by signaling thereby dynamically set the channel. By using the SVC, the connection can be set without relying on the manual operation of the operator, the connection can be released when the connection is not used, and the route can be also reselected in accordance with the network condition.
Recently, as one of new connections, there is SoftPVC. The SoftPVC is recommended in the ITU-T Q.2961 or in the Private Network-Network Interface Specification Version 1.0 (PNNI 1.0) of the ATM Forum Technical Committee.
With the SoftPVC, a computer referred to as xe2x80x9cNetwork Management Systemxe2x80x9d (NMS) that functions as a control unit of the STM or ATM network transmits point information indicating an initial point (call-out node) and a terminal point (call-in node) of the path to the call-out node. Then, a path from the call-out node to the call-in node is set by the similar signaling procedure as in the SVC.
As described above, with the conventional SoftPVC, by specifying the point information of the call-out node and the call-in node, the path between these nodes (connection) is automatically set. As a result, it is not necessary for the operator to input manually the information associated with the path to the call-out node, the call-in node and the relay node between these. Hence, the connection time of the path can be shortened.
With the conventional SoftPVC, the NMS notifies only the point information of the call-out node and the call-in node to the call-out node, and the call-out node sets the path from the call-out node to the call-in node by the similar signaling procedure as in the SVC, using the point code of the call-in node (telephone number of the call-in node, and the channel information of the call-in node (VCI/VPI, channel number or the like)) included in the notified point information.
With this method, only the point information of the call-out node and the call-in node is provided to the call-out node, as the point information for signaling. Therefore, if there are a plurality of routes from the call-out node via an relay node to the call-in node, an optional route in accordance with the selection algorithm of the route preset in the relay node is automatically selected from the plurality of routes.
As a result, with the conventional SoftPVC, a path from the call-out node to the call-in node passing through a specific point that the network manager intends to use cannot be set. On the contrary, it is also not possible to set a path from the call-out node to the call-in node, without passing through a specific point. That is to say, with the conventional SoftPVC, it is not possible to select a route that the network manager wants to use to set a path.
Therefore, paths may be concentrated on a certain node, depending upon the selection algorithm of the relay node, causing a problem in that load is concentrated on that node. Moreover, even if maintenance work for the node and the transmission line (channel) is required, a path avoiding the node and the transmission line to be subjected to the maintenance work cannot be set by the SoftPVC.
It is an object of the present invention to provide a network system that can set a path from a call-out node to a call-in node in a desired route by signaling.
In order to achieve the above object, the present invention has a construction described below. That is to say, the present invention is a network system comprising a network having a plurality of nodes and having a plurality of routes from a call-out node via an relay node to a call-in node, and a control unit for this network. When the call-out node and the call-in node are connected, passing through at least one node, the control unit provides to the call-out node a path connection request having node information stored therein, comprising: information associated with the call-out node; information associated with the call-in node; and information associated with a specified relay node specified as a node for the path to pass therethrough. Upon reception of the path connection request from the control unit, the call-out node generates a path connection start request comprising the node information in the path connection request, and transmits the path connection start request to the adjacent node so that the specified relay node receives the path connection start request, based on the information associated with the specified relay node, as well as setting a path with the adjacent node. Upon reception of the path connection start request, if there is a specified relay node which has not received the path connection start request, the above-described each node transmits the path connection start request to the adjacent node so that the aforesaid specified relay node receives the path connection start request, based on the information associated with the specified relay node. If all of the specified relay nodes have received the path connection start request, each node transmits the path connection start request to the adjacent node so that the call-in node receives the path connection start request based on the information associated with the call-in node, to thereby set a path with the adjacent node that has transmitted the path connection start request.
According to the present invention, since the path connection start request (SETUP message) reaches to the call-in node from the call-out node through the specified relay node by means of the above operation, a path passing through the specified relay node can be set by the signaling procedure.
Moreover, the present invention is a network system comprising a network having a plurality of nodes and having a plurality of routes from a call-out node via an relay node to a call-in node, and a control unit for this network. When the call-out node and the call-in node are connected without passing through at least one specific node, the control unit provides to the call-out node a path connection request having node information stored therein, comprising: information associated with the call-out node; information associated with the call-in node; and information associated with a specified non-passage node specified as a specific node through which the path does not pass. Upon reception of the path connection request from the control unit, the call-out node generates a path connection start request comprising the node information in the path connection request, and transmits the path connection start request to the adjacent node that does not correspond to the specified non-passage node based on the information associated with the specified non-passage node, as well as setting a path with the adjacent node. Upon reception of the path connection start request, if there is an adjacent node corresponding to the call-in node, the above described each node transmits the path connection start request to the adjacent node. If there is an adjacent node that does not correspond to the call-in node and the specified non-passage node, each node transmits the path connection start request to the adjacent node, and sets a path with the adjacent node that has transmitted the path connection start request.
According to the present invention, since the path connection start request (SETUP message) reaches the call-in node from the call-out node without passing through the specified non-passage node, a path that does not pass through the specified non-passage node can be set by the signaling procedure.
With the present invention, the aforesaid management unit can obtain the information associated with a path set from a call-out node to a call-in node from the network. The information associated with the path is, for example, connection information of each relay node (output line information, or input line information and output line information associated with the path).
Moreover, with the present invention, in the case of changing the set path, the management unit provides to the call-out node a path changeover request having alternative node information stored therein, comprising information associated with the call-out node; information associated with the call-in node; and information associated with a specified relay node of an alternative path. The call-out node cuts off the set path by transmitting a release message towards the call-in node, and prepares a path connection start request of the alternative path comprising the alternative node information. The respective nodes comprising the call-out node execute the processing according to a first aspect in response to the path connection start request of the alternative path, to thereby set the alternative path passing through a specified relay node.
In this manner, an old path may be cut off by a single instruction from the management unit and a new path (alternative path) passing through a specified relay node may be set, that is, the path can be changed.
Furthermore, with the present invention, in the case of changing the set path, the management unit provides to the call-out node a path changeover request having alternative node information stored therein, comprising information associated with the call-out node; information associated with the call-in node; and information associated with a specified non-passage node of the alternative path. The call-out node cuts off the set path by transmitting a release message towards the call-in node, and prepares a path connection start request of the alternative path comprising the alternative node information. The respective nodes comprising the call-out node execute the processing according to a fourth aspect in response to the path connection start request of the alternative path, to thereby set the alternative path which does not pass through a specified non-passage node.
In this manner, an old path may be cut off by a single instruction from the management unit and a new path (alternative path) which does not pass through a specified non-passage node may be set, that is, the path can be changed.